Device for producing an unvulcanized rubber member for tire manufacturing

ABSTRACT

The present invention provides an unvulcanized rubber member for tire manufacturing. The member forms at least a portion of a green tire, and features: multiple rib-protrusions that extend in a direction corresponding to a circumferential direction of the tire, and multiple grooves that extend in a direction corresponding to a radial direction of the tire and intersect the rib-protrusions. In accordance with the present invention, during vulcanization of the tire, the unvulcanized rubber member for tire manufacturing can efficiently expel air at the interior of the unvulcanized tire and between the unvulcanized tire and a vulcanizing mold.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an unvulcanized rubber member for tiremanufacturing, a device for producing the unvulcanized rubber member fortire manufacturing, and a method of producing the unvulcanized rubbermember.

2. Description of the Related Art

When a molded unvulcanized tire is charged into a vulcanizing mold andthen vulcanized, defects referred to as “lights” may appear on thesurface of a fabricated tire after vulcanization. As a result, a problemis caused in that the external appearance of the fabricated tiredeteriorates and the commercial value thereof decreases. “Lights” aregenerally produced due to air remaining between the unvulcanized tireand the vulcanizing mold.

Further, when a molded unvulcanized tire is charged into a vulcanizingmold and then vulcanized, a defect may occur in that air remains at theinterior of the fabricated tire after vulcanization. Due to this defector air void, a problem is caused in that performance and quality of thefabricated tire are deteriorated and the commercial value of thefabricated tire is decreased. Such a defect i.e., production of air voidis caused because air remains between members for structuring the tire(which members will be referred to as “tire structuring members”hereinafter), during assembling of the tire structuring members andmolding of the unvulcanized tire.

Conventionally, in order to solve these problems, methods such as thosedescribed below and the like have been attempted to prevent lights frombeing produced on the surface of a fabricated tire and prevent air voidfrom being formed at the interior of the fabricated tire by promotingbleeding of residual air:

-   (1) a plurality of vent holes for air-bleeding are provided inside a    vulcanizing mold;-   (2) outside coatings, which contain solid fillers for air-bleeding,    are applied to the surface of an unvulcanized tire;-   (3) a plurality of protrusions or grooves having predetermined size    and predetermined pitch are linearly formed, in a circumferential    direction of the tire, on the surface of a tire structuring member    to be used at the side of the surface of the tire (as disclosed in    Japanese Patent Application Laid-Open (JP-A) No. 60-143944);-   (4) a plurality of grooves having predetermined pitch and    predetermined size are linearly formed, in a radial direction of the    tire, on the surface of the tire structuring member to be used at a    side of a surface of the tire (as disclosed in Japanese Patent    Application Laid-Open (JP-A) No. 10-67056); and-   (5) air remaining between the tire structuring members is pushed out    by “stitching” the members by a metal or rubber roller during    assembly;    -   In reality, however, the conventional methods described above        have caused such problems as those described below:-   In the method of (1), that is, in providing a plurality of vent    holes, a great deal of expense is required, a lot of spews remain on    the surface of the fabricated tire after vulcanization, much time    and labor is required to remove the spews, and the external    appearance of the fabricated tire is damaged;-   In the method of (2) of applying the outside coatings, a specific    device for the application and considerable expense for coating are    necessitated i.e., the coating process thereof is quite time and    labor consuming;-   In the method of (3) of forming linear protrusions or grooves in the    tire circumferential direction, air cannot be bled efficiently from    the tire surface because irregularities located along the    circumferential direction of the vulcanizing mold or located along a    radial direction of the unvulcanized tire hinder bleeding, by way of    the linear protrusions or grooves, of the air remaining between the    unvulcanized tire and the vulcanizing mold during the vulcanization    of the tire;-   In the method of (4) of forming linear grooves in the tire radial    direction, in order to bleed the air efficiently, it is necessary to    form the grooves at considerably fine pitches, whereby a large    device and thus a large space are required, which is costly; and-   In the method of (5), it is impossible to conduct efficient bleeding    of the air remaining between the tire structuring members by    roll-stitching, because most of the tire structuring members for the    unvulcanized tire have high tackiness.

SUMMARY OF THE INVENTION

In view of the aforementioned facts, an object of the present inventionis to provide an unvulcanized rubber member for tire manufacturing, inwhich air at the interior of an unvulcanized tire and/or air between theunvulcanized tire and a vulcanizing mold can be efficiently expelledduring tire vulcanization, and a device for producing the unvulcanizedrubber member for tire manufacturing.

In order to accomplish the aforementioned objects, a first aspect of thepresent invention provides an unvulcanized rubber member for tiremanufacturing, which member is for forming at least a portion of a greentire, the member comprising: a plurality of rib-protrusions that extendin a direction corresponding to a circumferential direction of the tire;and a plurality of grooves that extend in a direction corresponding to aradial direction of the tire and intersect the rib-protrusions.

Description of operation of the unvulcanized rubber member for tiremanufacturing according to the first aspect of the present inventionwill be given hereinafter.

When the rib-protrusions that extend in the circumferential direction ofthe tire and the grooves that extend in the radial direction of the tireare provided in the unvulcanized rubber member for tire manufacturing soas to intersect each other, a deficiency in that directions in which airis expelled are limited during vulcanization is mitigated, whereby airremaining at the interior of the green tire and air between the greentire and the vulcanizing mold are allowed to be expelled efficiently.

In accordance with a second aspect of the present invention, each of therib-protrusions comprises a pitch of 2 to 15 mm, a height of 0.05 to 0.5mm, and a width of 0.2 to 1.5 mm.

Description of operation of the unvulcanized rubber member for tiremanufacturing according to the second aspect of the present inventionwill be given hereinafter.

If the pitch of the rib-protrusions is less than 2 mm, in a case inwhich the rib-protrusion is of a type molded by grooves formed at a dieprovided at an extruder for extrusion molding, the grooves will bedisposed too close to one another, thus making it difficult to form theprotrusion into the desired configuration. On the other hand, if thepitch of the protrusions is more than 15 mm, an interval between theprotrusions will be excessively large, significantly deteriorating theeffects of air-bleeding.

If the height of each of the rib-protrusions is less than 0.05 mm, theprotrusion will collapse at the initial stage after starting tirevulcanization, whereby the effects of air-bleeding is significantlydeteriorated. On the other hand, if the height of the rib-protrusionexceeds 0.5 mm, marks of the protrusions will be produced on afabricated tire after vulcanization, causing problems to the externalappearance of the fabricated tire.

Further, if the width of the rib-protrusion is less than 0.2 mm, an airpassage formed at a side of the rib-protrusion at the initial stageafter starting the tire vulcanization will be narrower, whereby theeffects of air-bleeding is significantly deteriorated. Also, if thewidth of the rib-protrusion exceeds 1.5 mm, the air passage formed atthe side after the rib-protrusion at the initial stage of starting thetire vulcanization will be narrower, whereby the effects of air-bleedingis significantly deteriorated.

In accordance with a third aspect of the present invention, each of thegrooves of the unvulcanized rubber member for tire manufacturing of thefirst or second aspect of the present invention, comprises a pitch of 2to 15 mm, a height of 0.05 to 0.5 mm, and a width of 0.2 to 1.5 mm.

Description of operation of the unvulcanized rubber member for tiremanufacturing according to the third aspect of the present inventionwill be given hereinafter.

If the pitch of the grooves is less than 2 mm, in a case in which thegrooves are formed by an embossing roller having ribs for forminggrooves at an outer circumference thereof, the ribs will be disposed tooclose to one another, thus making it difficult to form the grooves intoa desired configuration. On the other hand, if the pitch of the groovesis more than 15 mm, an interval between the grooves is excessivelylarge, whereby the effects of air-bleeding is significantlydeteriorated.

If the depth of each groove is less than 0.05 mm, the groove will befilled up at the initial stage after starting the tire vulcanization,whereby the effects of air-bleeding is significantly deteriorated. Onthe other hand, if the depth of the groove exceeds more than 0.5 mm,marks of grooves will be produced on the fabricated tire aftervulcanization, causing problems to the external appearance of thefabricated tire.

If the width of the groove is less than 0.2 mm, the groove will befilled up at the initial stage after starting the tire vulcanization,whereby the effects of air-bleeding is significantly deteriorated. Onthe other hand, if the width of the groove is more than 1.5 mm, a middleportion of the groove will rise to a shallow depth, whereby the effectsof air-bleeding is decreased.

A fourth aspect of the present invention provides a device for producingan unvulcanized rubber member for tire manufacturing of theabove-mentioned first aspect, the device comprising: an extruderincluding a die for continuously extruding the unvulcanized rubbermember, the die including notches for forming a plurality ofrib-protrusions on the unvulcanized rubber member, which rib-protrusionsextend in a direction corresponding to a circumferential direction ofthe tire; conveying apparatus disposed to receive the unvulcanizedrubber member from the extruder and convey the unvulcanized rubbermember in the extrusion direction of the unvulcanized rubber member; anda roller disposed to rotate while pressing a surface of the unvulcanizedrubber member being conveyed by the conveying apparatus, the rollerincluding an outer circumferential surface with protruding portions forforming a plurality of grooves in the unvulcanized rubber member, whichgrooves extend in a direction corresponding to a radial direction of thetire and intersect the rib-portions.

Description of operation of a pneumatic tire according to the fourthaspect of the present invention will be made hereinafter.

First, the unvulcanized rubber member is continuously extruded from theextruder. When the unvulcanized rubber member passes through the die ofthe extruder, multiple rib-protrusions, which extend in the directioncorresponding to the circumferential direction of the tire, are formedon the surface of the rubber member by the operation of the notchesformed at the die of the extruder.

The unvulcanized rubber member having the rib-protrusions formed on thesurface thereof is conveyed in a lengthwise (or extrusion) direction ofthe rubber member by the conveying device.

The roller having multiple protrusions formed at the outercircumferential surface thereof is pressed to roll on the surface of theunvulcanized rubber member being conveyed, and multiple grooves areformed on the surface of the unvulcanized rubber member having therib-protrusions formed thereon, to thereby continuously obtain theunvulcanized rubber member having multiple rib-protrusions and multiplegrooves intersecting the rib-protrusions formed thereon.

A fifth aspect of the present invention provides a method for producingan unvulcanized rubber member for tire manufacturing, the methodcomprising the steps of: (a) continuously extruding unvulcanized rubberthrough a die provided with notches, for forming an unvulcanized rubbermember with a plurality of rib-protrusions thereon, whichrib-protrusions extend in a direction corresponding to a circumferentialdirection of the tire; (b) conveying the unvulcanized rubber member inthe extrusion direction thereof; and (c) during the step of conveying,pressing the unvulcanized rubber member to form a plurality of groovestherein, which grooves extend in a direction corresponding to a radialdirection of the tire and intersect the rib-portions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic perspective view of a green tire (a portionthereof is shown) structured by using an unvulcanized rubber member fortire manufacturing according to the present invention;

FIG. 1B is a schematic perspective view of the entire green tireincluding the portion shown in FIG. 1A;

FIG. 2 is a perspective view of a sidewall portion structural member ofthe green tire in FIG. 1A;

FIG. 3 is a perspective view of a belt-cushion portion structural memberof the green tire in FIG. 1A;

FIG. 4 is a perspective view of a bead-reinforcement portion structuralmember of the green tire in FIG. 1A;

FIG. 5 is a front view of a die which is a portion of a device forproducing the unvulcanized rubber member for tire manufacturingaccording to the present invention; and

FIG. 6 is a perspective view of a roll which is a portion of the devicefor producing the unvulcanized rubber member for tire manufacturingaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1A shows a cross section of a green tire 10 prior to vulcanization.In FIG. 1A, there are shown a sidewall portion structural member 12, abelt-cushion portion structural member 14, a bead-reinforcement portionstructural member (bead filler) 16, a tread portion structural member18, a carcass 20, a belt 22, and a bead core 24. Further, FIG. 1B is aschematic perspective view of the entire green tire including theportions shown in FIG. 1A (however, only structures necessary tounderstand FIG. 1A are shown).

As shown in FIG. 2, a plurality of grooves 28 which extend along adirection corresponding to a radial direction of a tire (direction ofarrow X), and a plurality of rib-protrusions 30 that intersect thegrooves 28 and extend in a direction corresponding to a circumferentialdirection of the tire (direction of arrow Y) are formed on a surface ofthe sidewall portion structural member 12 formed of unvulcanized rubber(i.e., a surface of the side wall portion structural member that is tobe an outer surface of a fabricated tire). Note that FIG. 2 is anillustrative and explanatory view in which the grooves 28 and therib-protrusions 30 are greatly enlarged in order to elucidate thesidewall portion structural member 12.

It is preferable that the grooves 28 have a pitch p1 of 2 to 15 mm, adepth d of 0.05 to 0.5 mm, and a width w1 of 0.2 to 1.5 mm.

Although each groove 28 of FIG. 2 is formed into a quadrilateralcross-sectional configuration in the present embodiment, it can beformed into another configuration, such as a triangular or semi-circularconfiguration.

It is preferable that the rib-protrusions 30 have a pitch p2 of 2 to 15mm, a height h of 0.05 to 0.5 mm, and a width w2 of 0.2 to 1.5 mm.

Although each rib-protrusion 30 (of FIG. 2) is formed into a triangularcross-sectional configuration in the present embodiment, it can beformed into another configuration, such as a quadrilateral orsemi-circular configuration.

The grooves 28 are formed continuously at portions of intersection ofthe grooves 28 and the rib-protrusions 30.

As shown in FIG. 3, a plurality of grooves 32 which extends along adirection corresponding to the radial direction of a tire, and aplurality of rib-protrusions 34 that intersect the plurality of thegrooves 32 and extends in a direction corresponding to thecircumferential direction of the tire are formed on a surface of thebelt-cushion portion structural member 14 formed of unvulcanized rubber(i.e., on a surface of the member 14, adhered to the carcass 20).

It is preferable that the grooves 32 have pitch, depth, and width of thesame sizes as the pitch p1, the depth d and the width w1 of theabove-described grooves 28, and it is also preferable that therib-protrusions 34 have pitch, width, and height of the same sizes asthe pitch p2, the height h and the width w2 of the above-describedrib-protrusions 30.

As shown in FIG. 4, a plurality of grooves 36 which extend along adirection corresponding to the radial direction of the tire, and aplurality of rib-protrusions 38 that intersect the plurality of thegrooves 36 and extend in a direction corresponding to thecircumferential direction of the tire are formed on a surface of thebead-reinforcement portion structural member 16 formed of unvulcanizedrubber (i.e., surface of the member 16 that is to be adhered to thecarcass 20).

It is preferable that the grooves 36 have pitch, depth, and width of thesame sizes as the pitch p1, the depth d and the width w1 of theabove-described groove 28, and it is also preferable that therib-protrusions 38 have pitch, width, and height of the same sizes asthe pitch p2, the height h and the width w2 of the above-describedrib-protrusions 30.

An example of a method for forming the grooves 28 and therib-protrusions 30 of the sidewall portion structural member 12 will beexplained hereinafter (and description of a method of forming thegrooves 32 and the rib-protrusions 34 of the belt-cushion portionstructural member 14 and a method of forming the grooves 36 and therib-protrusions 38 of the bead-reinforcement portion structural member16 will be omitted, because these two methods are basically the same asthe method for forming the grooves 28 and the rib-protrusions 30).

Ordinarily, the sidewall portion structural member 12 can beextrusion-molded by an extruder and, as shown in FIG. 5, it is desirablethat grooves 42 are formed beforehand at a die of the extruder, suchthat the grooves 42 have shapes complementary to the shapes of therib-protrusions 30. Accordingly, the sidewall portion structural member12 having the rib-protrusions 30 formed thereon can be formedcontinuously.

Next, the sidewall portion structural member 12 having therib-protrusions 30 formed thereon is continuously conveyed by a conveyoror the like in a lengthwise or extrustion direction. A roll 46, which isshown in FIG. 6 and has ribs 44 formed at an outer circumferentialsurface thereof, is pressed to roll on the surface of the sidewallportion structural member 12 being conveyed.

Consequently, the grooves 28 and the rib-protrusions 30 shown in FIG. 2can be formed continuously on the surface of the sidewall portionstructural member 12.

Operation

Description of operation of the present embodiment will be givenhereinafter.

In the green tire 10, since the grooves 28 extending in the tire radialdirection and the rib-protrusions 30 extending along the tirecircumferential direction are present together at tire side portions, itis possible to form a lot more passages through which undesired air thatis remained between a tire surface and an inner surface of the mold canbe expelled during molding of the green tire in the mold, whereby it ispossible to overcome a conventional deficiency that air-bleedingdirections are limited.

In the present invention, the undesired air remaining between the tiresurface and the inner surface of the mold can be distributed in thesufficiently wide and shallow manner, so that the rubber can reliablyabsorb the air ultimately remained between the tire surface and theinner surface of the mold, whereby lights, which is generated by arelatively large amount of accumulation of localized air, are preventedfrom being formed at the surface of the fabricated tire.

When the belt-cushion portion structural member 14 is stuck to thecarcass 20, air that is liable to be pooled between the belt-cushionportion structural member 14 and the carcass 20 can be let out throughthe grooves 32 and the rib-protrusions 34. Even when air stays betweenthe belt-cushion portion structural member 14 and the carcass 20, theair can easily be expelled via the grooves 32 and the rib-protrusions 34by applying pressure to the air during the molding of the tire.

When the bead-reinforcement portion structural member 16 is stuck to thecarcass 20, air that is liable to be pooled between thebead-reinforcement portion structural member 16 and the carcass 20 canbe let out through the grooves 36 and the rib-protrusions 38. Even whenair stays between the bead-reinforcement portion structural member 16and the carcass 20, the air can easily be expelled via the grooves 36and the rib-protrusions 38 by applying pressure to the air during themolding of the tire.

Therefore, generation of air residue between the tire structuringmembers can be reliably prevented.

If the pitch p1 of the grooves 28 is less than 2 mm, the ribs 44 of theroll 46 have to be put excessively close to one another, thereby makingit difficult to form the grooves in the desired configuration. If thepitch p1 of the grooves 28 exceeds 15 mm, an interval between thegrooves will be excessively large, thereby deteriorating theair-bleeding effect.

If the depth d of the grooves 28 is less than 0.05 mm, the grooves 28will be filled up at the initial stage after starting tirevulcanization, whereby the air-bleeding effect is significantlydeteriorated. If the depth d of the grooves 28 exceeds 0.5 mm, marks ofthe grooves 28 will be produced on the fabricated tire aftervulcanization, causing problems to the external appearance of thefabricated tire.

If the width w1 of the grooves 28 is less than 0.2 mm, the grooves 28will be filled up at the initial stage after starting the tirevulcanization, whereby the air-bleeding effect is significantlydeteriorated. If the width w1 of the grooves 28 exceeds 1.5 mm, middleportions of the grooves 28 will rise at a shallow depth, whereby theair-bleeding effect is decreased.

If the pitch p2 of the rib-protrusions 30 is less than 2 mm, the groovesformed at the die, which is equipped at the extruder for extrusionmolding, will be put excessively close to one another, making itdifficult to form the protrusions into the desired configuration. If thepitch p2 exceeds 15 mm, an interval between the protrusions will beexcessively large, whereby the air-bleeding effect is significantlydeteriorated.

If the height h of the rib-protrusions 30 is less than 0.05 mm, theprotrusions will collapse at the initial stage after starting the tirevulcanization, whereby the air-bleeding effect is significantlydeteriorated. If the height h exceeds 0.5 mm, marks of the protrusionswill be produced on the fabricated tire after vulcanization, therebycausing problems to the external appearance of the fabricated tire.

If the width w2 of the rib-protrusions 30 is less than 0.2 mm, airpassages formed at the sides of the rib-protrusions 30 at the initialstage after starting the tire vulcanization will be narrower, wherebythe air-bleeding effect is significantly deteriorated. If the width w2exceeds 1.5 mm, the air passages formed at the sides of therib-protrusions 30 at the initial stage after starting the tirevulcanization will be narrower, whereby the air-bleeding effect issignificantly decreased.

In the above-described embodiment of the present invention, the grooves28 and the rib-protrusions 30 can be formed continuously on the surfaceof the sidewall portion structural member 12, as shown in FIG. 2.

Further, in the above-described embodiment of the present invention, thegrooves and rib-protrusions are formed on the sidewall portionstructural member 12, the belt-cushion portion structural member 14, andthe bead-reinforcement portion structural member 16. However, thepresent invention is not limited to this, and grooves andrib-protrusions can be formed on others of the unvulcanized rubbermembers for tire manufacturing.

As described above, according to the unvulcanized rubber member for tiremanufacturing of the present invention, an excellent effect is providedin that air at the interior of the unvulcanized tire and air between theunvulcanized tire and the vulcanizing mold can be effectively expelled.

Further, according to the device for producing the unvulcanized rubbermember for tire manufacturing of the present invention, an excellenteffect is provided in that the unvulcanized rubber member for tiremanufacturing, in which the air at the interior of the unvulcanized tireand the air between the unvulcanized tire and the vulcanizing mold canbe efficiently expelled, is produced efficiently.

1. An unvulcanized rubber member for tire manufacturing, which member isfor forming at least a portion of a green tire, the member comprising: aplurality of rib-protrusions that extend in a direction corresponding toa circumferential direction of the tire; and a plurality of grooves thatextend in a direction corresponding to a radial direction of the tireand intersect the rib-protrusions.
 2. The member according to claim 1,wherein each of the rib-protrusions comprises a pitch of 2 to 15 mm, aheight of 0.05 to 0.5 mm, and a width of 0.2 to 1.5 mm.
 3. The memberaccording to claim 1, wherein each of the grooves comprises a pitch of 2to 15 mm, a height of 0.05 to 0.5 mm, and a width of 0.2 to 1.5 mm. 4.The member according to claim 1, wherein, at portions at which thegrooves and the rib-protrusions intersect, the grooves are formedcontinuously.
 5. The member according to claim 1, wherein theunvulcanized rubber member for tire manufacturing comprises a sidewallportion structural member.
 6. The member according to claim 5, whereinthe sidewall portion structural member comprises an outer surface whichis to be an outer surface of the fabricated tire, and therib-protrusions and the grooves are formed on the outer surface of thesidewall portion structural member.
 7. The member according to claim 1,wherein the tire is to include a carcass and a belt, and theunvulcanized rubber member comprises a belt-cushion portion structuralmember to be disposed between the carcass and the belt.
 8. The memberaccording to claim 7, wherein the belt-cushion portion structural membercomprises a surface to be closely contacted with the carcass, and therib-protrusions and the grooves are formed on said surface.
 9. Themember according to claim 1, wherein the unvulcanized rubber membercomprises a bead-reinforcement portion structural member including abead filler.
 10. The member according to claim 9, wherein the tire is toinclude a carcass, the bead-reinforcement portion structural membercomprises a surface to be adhered with the carcass, and therib-protrusions and the grooves are formed on said surface. 11-19.(canceled)
 20. A method for producing an unvulcanized rubber member fortire manufacturing, the method comprising the steps of: (a) continuouslyextruding unvulcanized rubber through a die provided with notches, forforming an unvulcanized rubber member with a plurality ofrib-protrusions thereon, which rib-protrusions extend in a directioncorresponding to a circumferential direction of the tire; (b) conveyingthe unvulcanized rubber member in the extrusion direction thereof; and(c) during the step of conveying, pressing the unvulcanized rubbermember to form a plurality of grooves therein, which grooves extend in adirection corresponding to a radial direction of the tire and intersectthe rib-portions.